NEW YORK (CNN) -- A fourth Staten Island man pleaded guilty Monday to charges stemming from three assaults targeting African-Americans in the hours after Barack Obama was declared the winner in the November presidential election, authorities said.

Ralph Nicoletti, 18, was the last defendant to enter a plea. Michael Contreras, 18, Brian Carranza, 21, and Bryan Garaventa, 18, pleaded guilty in federal court in January to charges of conspiring to interfere with voting rights.

According to the indictment, the four "knowingly and intentionally" conspired to intimidate African-Americans for exercising their right to vote. Contreras, Carranza and Garaventa could be sentenced to 10 years in prison, while as part of his plea, "Nicoletti has agreed to a sentence of 12 years, subject to the approval of the court," the U.S. Department of Justice said in a news release.

Attorneys for the men declined to comment.

Prosecutors said in a court filing that the defendants were at a "makeshift outdoor clubhouse" in the Rosebank section of Staten Island on November 4 when they learned of Obama's victory. At that point, prosecutors said, Nicoletti drove Contreras, Carranza and Garaventa to the predominantly African-American Park Hill neighborhood in Staten Island.

Their purpose, prosecutors said, was to assault African-Americans because of Obama's win.

Their first victim, according to the U.S. Attorney's Office, was Ali Kamara, 17, whom they beat with a metal pipe and a collapsible police baton. Kamara escaped after suffering a concussion and injuries to his legs.

"The first swing that swung -- it hit my head. It cut my head," Kamara told CNN affiliate WABC. "I got staples on my head now." He escaped by hiding in a neighbor's back yard until the attackers moved on.

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Continuing to the Port Richmond section of Staten Island, also predominantly African-American, the group allegedly assaulted an unidentified African-American man, who was pushed to the ground, the Justice Department said.

The group's final assault, authorities said, targeted Ronald Forte, a man they mistakenly believed to be African-American who was walking along Blackford Avenue in the Port Richmond neighborhood. Forte, who is white, was wearing a hoodie that prevented the teenagers from identifying his race.

According to the indictment, the four teens decided to assault Forte with the police baton as they drove by, but at the last moment Nicoletti swerved the vehicle directly into Forte instead. Forte was thrown onto the hood of the car, shattering the front windshield and suffering traumatic head injuries.

The court filing also says that several weeks ago, Nicoletti and three others attacked Contreras, accusing him of cooperating with authorities. There was no immediate indication if separate charges were filed as a result of that incident.

Contreras, Carranza and Garaventa have been released on bail, but the judge ordered they remain under supervision, a representative of the U.S. District Attorney's Office told CNN, and Nicoletti remains in jail.